Schiff Base Proton Acceptor Assists Photoisomerization of Retinal Chromophores in Bacteriorhodopsin
| Autor: | Chih Chang Hung, Takayoshi Kobayashi, Chii Shen Yang, Xiao Ru Chen, Atsushi Yabushita, Ying Kuan Ko |
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| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Proton Photoisomerization Biophysics Photochemistry Vibration 03 medical and health sciences chemistry.chemical_compound Isomerism Escherichia coli Schiff Bases Halobacteriaceae Schiff base Sequence Homology Amino Acid 030102 biochemistry & molecular biology biology Lasers Spectrum Analysis Proteins Hydrogen Bonding Bacteriorhodopsin Retinal Chromophore Photochemical Processes 030104 developmental biology chemistry Bacteriorhodopsins Mutation biology.protein Protons Isomerization |
| Zdroj: | Biophysical Journal. 112:2503-2519 |
| ISSN: | 0006-3495 |
| Popis: | In this study, we investigated the ultrafast dynamics of bacteriorhodopsins (BRs) from Haloquadratum walsbyi (HwBR) and Haloarcula marismortui (HmBRI and HmBRII). First, the ultrafast dynamics were studied for three HwBR samples: wild-type, D93N mutation, and D104N mutation. The residues of the D93 and D104 mutants correspond to the control by the Schiff base proton acceptor and donor of the proton translocation subchannels. Measurements indicated that the negative charge from the Schiff base proton acceptor residue D93 interacts with the ultrafast and substantial change of the electrostatic potential associated with chromophore isomerization. By contrast, the Schiff base proton donor assists the restructuring of the chromophore cavity hydrogen-bond network during the thermalization of the vibrational hot state. Second, the ultrafast dynamics of the wild-types of HwBR, HmBRI, and HmBRII were compared. Measurements demonstrated that the hydrogen-bond network in the extracellular region in HwBR and HmBRII slows the photoisomerization of retinal chromophores, and the negatively charged helices on the cytoplasmic side of HwBR and HmBRII accelerate the thermalization of the vibrational hot state of retinal chromophores. The similarity of the correlation spectra of the wild-type HmBRI and D104N mutant of HwBR indicates that inactivation of the Schiff base proton donor induces a positive charge on the helices of the cytoplasmic side. |
| Databáze: | OpenAIRE |
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